1. Field of the Invention
The present invention relates to hermetically sealed glass packages that are suitable to protect thin film devices that are sensitive to the ambient environment. Some examples of such devices are organic emitting light diode (OLED) displays, sensors, and other optical devices. The present invention is demonstrated using OLED displays as an example.
2. Description of Related Art
OLEDs have been the subject of a considerable amount of research in recent years because of their use and potential use in a wide variety of electroluminescent devices. For instance, a single OLED can be used in a discrete light emitting device or an array of OLEDs can be used in lighting applications or flat-panel display applications (e.g., OLED displays). The OLED displays are known as being very bright and having a good color contrast and wide viewing angle. However, the OLED displays and in particular the electrodes and organic layers located therein are susceptible to degradation resulting from interaction with oxygen and moisture leaking into the OLED display from the ambient environment. It is well known that the lifetime of the OLED display can be significantly increased if the electrodes and organic layers within the OLED display are hermetically sealed from the ambient environment. Unfortunately, in the past it was very difficult to develop a sealing process to hermetically seal the OLED display. Some of the factors that made it difficult to properly seal the OLED display are briefly mentioned below:                The hermetic seal should provide a barrier for oxygen (10−3 cc/m2/day) and water (10−6 g/m2/day).        The size of the hermetic seal should be minimal (e.g., <1 mm) so it does not have an adverse effect on size of the OLED display.        The temperature generated during the sealing process should not damage the materials (e.g., electrodes and organic layers) within the OLED display. For instance, the first pixels of OLEDs, which are located about 1 mm from the seal in the OLED display should not be heated to more than 85° C. during the sealing process.        The gases released during sealing process should not contaminate the materials within the OLED display.        The hermetic seal should enable electrical connections (e.g., thin-film chromium) to enter the OLED display.        
Today the most common way for sealing the OLED display is to use different types of epoxies with inorganic fillers and/or organic materials that form the seal after they are cured by ultra-violet light. Although these types of seals usually provide good mechanical strength, they can be very expensive and there are many instances in which they have failed to prevent the diffusion of oxygen and moisture into the OLED display. In fact, these epoxy seals need to use a desiccant to get an acceptable performance. Another potential way for sealing the OLED display is to utilize metal welding or soldering, however, the resulting seal can suffer from the problematical shorting of the electrical leads which enter the OLED display. This sealing process is also very complex since several thin film layers are necessary to get good adhesion. Accordingly, there is a need to address the aforementioned problems and other shortcomings associated with the traditional seals and the traditional ways for sealing the OLED displays. These needs and other needs are satisfied by the hermetic sealing technology of the present invention.